Crush-forming operation on grinding wheels



0d- 1 1 5. J. HARLEY ETAL CRUSH-FORMING OPERATION ON GRINDING WHEELS Filed Feb. 23, 1943 3 Sheets-Sheet l Oct. 10, 1944. 5. J. HARLEY EFAL CRUSH-FORMING OPERATION ON GRINDING WHEELS 3 Sheets-Sheet 2 Filed Feb. 23, 1943 l J2nr-enZon5:

ct. 10, 1944 s. J. HARLEY ETAL CRUSH-FORMING OPERATION 0N GRINDING WHEELS Filed Feb. 23, 1943 3 Sheet5-Sheec 5 T n llllllill 'IIH T Patented on. 10, 1944 CRUSH-FORMING GPERATION N GRINDING WHEELS Stanley .lafia Harley, Coventry, and John Ernest I Wainwright, Hunningham, England Application February 23, 1943, Serial No. 476,872

2 Claims. (Cl. 125-11) This invention relates to crush-forming operations on grinding wheels, and has for its ob- Ject to improve the efliciency of this method of shaping the operative surfaces thereof for usein form-grinding operations, such, for example, as the production of screw thread and gear tooth forms.

Where the required form on the wheel is thatof a peripheral annual rib of a cross-sectional shape appropriate to the purpose the wheel is intended to serve, the said form is sometimes produced by means of a single crushing. roller suitably grooved and. arranged with'its rotational axis parallel with that of the grinding wheel. The objection to the use of a single crushing roller is that the abrasive action produce thereby is harsh and not only in excess of that necessary to the crush-forming operation but also injurious to the crushing roller itself. The reason is due to two main factors. In the first place the peripheral speed relationship between the crushing roller and the grinding wheel is such that the maximum and minimum diam.- eters of the one run with the minimum and maximum diameters respectively of the other. In the second place the excessive abrasion caused by this peripheral speed relationship is accentuated by the prolonged retention of loose grit between the contacting surfaces.

The excessive abrasion produced by the single crushing roller has to a limited extent been reduced by the employment of a separate crushing roller for each flank of the required form on the grinding wheel. Such reduction as is obtained in this way is, however, small and not due to an improved peripheral speed relationship, which remains substantially the same as with the single roller, but to the fact that the loose grit removed from the wheel is not re-- tained between the contacting surfaces to the same extent as with the single roller.

According to the present invention the efllciency of crush-forming operations is materially increased by an arrangement which reduces the degree of abrasion produced to no more than is necessary for the crush-forming operation, with the beneficial results that former irregularities on the operative surfaces of the grinding wheel are in large part eliminated and at the same time the useful life of the crushing rollers is considerably extended.

The invention involves the use of at least two crushing rollers arranged one at each side of the grinding wheel, and consists in forming apex in the axis of the grinding wheel. By means of this arrangement the maximum and minimum diameters ofeach roller runs with the maximum and minimum diameters respectively of that part of the wheel with which the roller is in contact, so that the abrasive action is reduced to the permissible minimum with the beneficial effects aforesaid.

In. the accompanying drawings;

Figure 1 illustrates one embodiment of the invention in the crush-forming of a symmetrical form on a grinding wheel.

Figure 2 shows an alternative arrangement for a similar purpose.

Figure 3 shows the application of the invention in the crush-forming of an unsymmetrical form.

Figure 4 illustrates a further embodiment of the invention in which three crushing rollers are employed.

In each of the examples shown in the drawings (1 represents the rotatable grinding wheel and b, b and hthe crushing rollers.

Where, as shown in Figures 1 and 2, it is desired to form the wheel with an annular peripheral rib a of symmetrical V-shape in crosssection, the crushing rollers b, b at opposite sides of the grinding wheel d are each formed as a frustum of a cone having its apex in the axis A of the grinding wheel so that the minimum diameter of each roller runs with the minimum diameter of the rib on the wheel d and the maximum diameter of the roller runs with the maximum diameter of the wheel. By arranging the crushing rollers in this way not only is excessive abrasion and its deleterious effects avoided but the loose grit removed by the crushing operation is not retained between the contacting surfaces but is free to escape as quick- 1y 'as it is formed.

The same principle of peripheral speed relationship is adopted in cases where, as shown in Figure 3, the rib a to be produced on the wheel is of an unsymmetrical shape in cross-section. In this case each roller, b D is arranged in the manner above described and while having 'its peripheral surface shaped to produce the form required in the flank of the rib on the wheel it will also have its peripheral surface formed with extreme operative or grinding lateral portions lying at difierent distances radially fromthe axis of each said roller and which when connected by imaginary straight lines axially of said roller at .all points about each said roller will result in said imaginary straight lines converging and defining a cone having its apex lying in the axis of the grinding wheel, and those portions of said imaginary straight lines extending between said lateral portions and possibly projected through a convex portion of said peripheral surface and possibly spanning a depression in another portion oi. said peripheral surface will define the irustrum of said cone. As in Figures 1 and 2 so in this case the maximum and minimum diameters of each roller will run with the maximum and minimum diameters respectively of the flanks of the rib with which they are respectively in contact. In the case of the left-hand roller there may be a little more abrasion than in the case of the right-hand roller by reason of the concave portion of the former having a tendency to retain loose grit but in either case will the degree of abrasion be such as to cause appreciable wear on the roller or any appreciable irregularities in the surface on the wheel.

Figure 4 illustrates a further adaptation of the present invention. In this case the peripheral surfaces of the rollers b, b arranged as before, are convexlycurved in a transverse direction to produce con-cave flanks on the wheel nb (1 Here also the peripheral speed relationship is such that the maximum and minimum diameters of the crushing rollers run with the maximum and minimum diameters of the flanks of the rib on the 7 wheel. A third crushing roller may, if required,

be employed to form the crest of the rib, said third roller being rotatably mounted about an axis parallel with the rotational axis of the grinding wheel d.

In every case the crushing rollers are adjustably mounted on a slide i which is itself adjustable for feed purposes in a direction at right angles to the axis of the grinding wheel by means of a screw m having a calibrated head n. For this purpose each roller is rotatably mounted on a spindle e secured to a carrier 1. In the arrangement shown in Figure 1 the angular positions.

of the rollers with respect 'to the grinding wheel is determined by adjusting the carriers along arcuate guide slots 0 in the slide and securing them in the adjusted position by means of nuts 7' on bolts k having T-heads engaging the appropriately lormed slots. The centre of curvature of said slots lies at the intersection 1' oi the midplanes of the rollers in the mid-plane of the grinding wheel. The rollers are also adjustable towards and away from the wheel in a direction at right angles to their axis of rotation, this adjustment being provided for and limited by slots 1 in the carriers through which the locking bolts it pass.

Alternatively, as shown in Figures'2, 3 and 4, the adjustment of the rollers towards and away from the wheel in a direction at right angles to their axes of rotation may be obtained by mounting the carriers f on appropriately inclined surfaces h on the slide 1, the carriers, as before, being suitably slotted for the locking bolts k.

In Figure 4 the third roller 0 can either be arranged for independent adjustment towards the wheel, on the slide 1' or adjustable simultaneously with the crushing rollers b, b".

We claim:

1. Apparatus for forming the periphery of grinding wheels by the crushing method, comprising a pair of crushing rollers arranged one at each side of the grinding wheel, each of said rollers forming the frustum of a cone having its apex in the axis of the grinding wheel, a slide adapted for adjustment on the grinding machine for feeding said rollers to the grinding wheel thereof and having arcuate guide slots, a carrier for each of said rollers angularly adjustable on said slide in said slots, and means for adjusting said carriers in a direction at right angles to the rotational axis of their respective rollers.

2. Apparatus for forming the periphery of grinding wheels by the crushing method, comprising a pair of crushing rollers arranged one at each side of the grinding wheel, each of said rollers forming the frustum of a cone having its apex in the axis of the. grinding wheel, a slide adapted for adjustment on the grinding machine for feeding said rollers to the grinding wheel thereof, a carrier for each of said rollers, means for adjusting the angular position of said carriers on said slide, and means for adjusting said carriers in a direction at right angles to the rotational axes of their respective rollers.

STANLEY JAFFA HARLEY. JOHN ERNEST WAINWRIGHT. 

